RSCC Precharge Control for Soft-Switching PV Conversion Circuits
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Solution Overview
Problem
Conventional direct current converters suffer from high switch losses and low power density due to hard switching states and the use of large magnetic elements, which affect their efficiency and performance, particularly in applications like photovoltaic systems.
Innovation Solution
A resonant switched capacitor converter (RSCC) with a control circuit that precharges the output filter and resonant units before operation, using a switch unit to transmit energy to these units, reducing the impact of initial current surges and maintaining efficient soft switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional direct current converter uses a magnetic element (inductor or transformer) to transfer energy, then the converter can operate, but the switch experiences large losses and operating efficiency is reduced
Solution Approach 1:
The patent extracts the magnetic element from the energy transfer path and replaces it with a resonant unit consisting of a resonant inductor and resonant capacitor. This removal of the conventional magnetic element eliminates the source of large switch losses while maintaining the energy transfer function through resonant oscillation.
Solution Approach 2:
The patent changes the operating parameters of the switch from hard switching to soft switching by introducing resonant oscillation. This parameter change allows the switch to operate at optimal points on its characteristic curves, minimizing conduction and switching losses while improving overall efficiency.
2Power
If a conventional direct current converter uses a magnetic element (inductor or transformer), then energy transfer is achieved, but the magnetic element has large volume and power density is low
Solution Approach 1:
The patent removes the large-volume conventional magnetic element and replaces it with a resonant unit that achieves the same energy transfer function with significantly reduced volume, thereby increasing power density.
Solution Approach 2:
The patent employs resonant oscillation - a periodic action - to transfer energy between the resonant inductor and resonant capacitor. This periodic energy exchange enables compact design while maintaining effective power transfer, as the resonant frequency allows efficient energy oscillation in a small volume.
3Reliability
If the RSCC enters operating state directly with output filter capacitor voltage approximately zero, then the converter can start operation, but the resonant inductor current causes impact to the power switching transistor affecting performance
Solution Approach 1:
The patent applies preliminary action by pre-charging the output filter capacitor before the RSCC enters its normal operating state. This preliminary charging prevents large inrush currents from the resonant inductor from impacting the power switching transistor, thereby protecting the transistor and improving reliability.
Solution Approach 2:
The patent implements beforehand cushioning by introducing a pre-charge circuit that limits and controls the current flowing into the output filter capacitor during startup. This cushioning mechanism protects the power switching transistor from harmful current impacts that would otherwise occur during direct startup.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures efficient operation of the RSCC by minimizing switch stress and maintaining high power density without additional costs or circuit size, thus enhancing the performance of the converter and associated systems.
Implementation Method 1
a resonant unit is used to transfer energy, so that a power switch device in the RSCC can operate in a soft switching state
Implementation Method 2
control the switch unit in the RSCC to transmit, to the output filter unit, electric energy supplied by the first power supply
Data Source
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AI summary
This application provides a conversion circuit, a conversion circuit precharge control method, and a photovoltaic system, to avoid additional costs, and avoid impact on a switch caused by a current generated in a circuit at a moment when an RSCC enters an operating state, thereby ensuring operating performance of the RSCC. The conversion circuit includes a first power supply, a resonant switched capacitor converter RSCC, and a control circuit. The RSCC includes a switch unit, an output filter unit, a first input end, a second input end, and an output end. The switch unit is connected between the first input end and the second input end. The output filter unit is connected between the second input end and the output end. One electrode of the first power supply is connected to the first input end, and the other electrode of the first power supply is connected to the second input end. The first power supply is configured to supply an input voltage to the RSCC. The control circuit is connected to the switch unit, and is configured to: before controlling the RSCC to operate, control the switch unit in the RSCC to transmit, to the output filter unit, electric energy supplied by the first power supply.